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10/20/2008 05:31:50 PM · #1 |
| Ok, maybe i am being really naive here, but recently i have preferred to use manual focus for everything as i feel i am in more control of what i do. I was then thinking.....how does focusing work? How does the camera know when your subject is in focus. It always amazes me everytime i press the shutter button half way down and focus. How does it know when to *beep*? How does it know your focused? |
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10/20/2008 05:33:37 PM · #2 |
It works on contrast; the more out of focus, the less contrast. Try it manually; point lens at something at closest focusing distance, and then watch it get grayer and grayer as you pull focus out.
This is why autofocus won't work on a plain blue sky, for example...
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10/20/2008 05:45:26 PM · #3 |
Originally posted by Bear_Music:
It works on contrast; the more out of focus, the less contrast. Try it manually; point lens at something at closest focusing distance, and then watch it get grayer and grayer as you pull focus out.
This is why autofocus won't work on a plain blue sky, for example...
R. |
Ahhh right, i see that makes sense. I was going to ask how does know when it has reaches optimum contrast then i realised that it must be calculating some sort of value. I know in my head what it does and i have tried to write it down but i just cannot explain it in such a way that it makes sense when i read it back to myself, but i do understand what you mean :) |
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10/20/2008 05:48:58 PM · #4 |
| Contrast detection is part of it. Decent write up on wikipedia. |
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